Feature Overview

The Frame Relay IP RTP Priority feature provides a strict priority queueing scheme on a Frame Relay permanent virtual circuit (PVC) for delay-sensitive data such as voice. Voice traffic can be identified by its Real-Time Transport Protocol (RTP) port numbers and classified into a priority queue configured by the frame-relay ip rtp priority command. The result of using this feature is that voice is serviced as strict priority in preference to other nonvoice traffic.

This feature extends the functionality offered by the ip rtp priority command by supporting Frame Relay PVCs. This feature allows you to specify a range of User Datagram Protocol (UDP) ports whose voice traffic is guaranteed strict priority service over any other queues or classes using the same output interface. Strict priority means that if packets exist in the priority queue, they are dequeued and sent first—that is, before packets in other queues are dequeued.

Benefits

The strict priority queueing scheme allows delay-sensitive data such as voice to be dequeued and sent first—that is, before packets in other queues are dequeued. Delay-sensitive data is given preferential treatment over other traffic. This process is performed on a per-PVC basis, rather than at the interface level.

Related Features and Technologies

The Frame Relay IP RTP Priority feature is related to the following features:

This feature runs on the platforms listed. However, it is most useful on voice supported platforms, such as the Cisco 2600 series, Cisco 3600 series, Cisco 7200 series, and Cisco 7500 Route Switch Processor (RSP) series.

Configuration Tasks

Configuring Frame Relay IP RTP Priority

To reserve a strict priority queue on a Frame Relay PVC for a set of RTP packet flows belonging to a range of UDP destination ports, use the following command in map-class configuration mode.

Note Because the frame-relay ip rtp priority command gives absolute priority over other traffic, it should be used with care. In the event of congestion, if the traffic exceeds the configured bandwidth, then all the excess traffic is dropped.

Configuration Examples

Frame Relay IP RTP Priority Configuration Example

The following example first configures the Frame Relay map class called voip and then applies the map class to PVC 100 to provide strict priority service to matching RTP packets:

map-class frame-relay voip

frame-relay cir 256000

frame-relay bc 2560

frame-relay be 600

frame-relay mincir 256000

no frame-relay adaptive-shaping

frame-relay fair-queue

frame-relay fragment 250

frame-relay ip rtp priority 16384 16380 210

interface Serial5/0

ip address 10.10.10.10 255.0.0.0

no ip directed-broadcast

encapsulation frame-relay

no ip mroute-cache

load-interval 30

clockrate 1007616

frame-relay traffic-shaping

frame-relay interface-dlci 100

class voip

frame-relay ip rtp header-compression

frame-relay intf-type dce

In this example, RTP packets on PVC 100 with UDP ports in the range 16384 to 32764 will be matched and given strict priority service.

Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and coincidental.